Electric motor control apparatus

ABSTRACT

A control apparatus for a multiphase AC electric motor having an inverter includes a current control including an abnormal-state current controller; an abnormal-state detector that detects an abnormal state of any of a wire of an electric motor, a wire of an inverter, and a wire connecting the electric motor to the inverter as an abnormal phase; and an abnormal phase disconnect. The abnormal phase disconnect disconnects one or more of phases detected to be in an abnormal-state and the abnormal-state current controller generates an abnormal state voltage command in accordance with detection of an abnormal state, and uses phases other than the disconnected phases of the inverter to control individual currents of the phases, with the abnormal-state voltage command used as a multiphase voltage command.

TECHNICAL FIELD

This invention relates to an electric motor control apparatus whichdrives an electric motor, and more particularly to a control apparatusfor an electric motor, in which even when any abnormality such asgrounding or short-circuiting has occurred in one phase or between thetwo phases of the multiphase electric motor or an inverter, the electricmotor can be driven by a control scheme suited to the abnormal state.

BACKGROUND ART

An example of a prior-art apparatus is, for example, an apparatus whichis disclosed in Patent Document 1 indicated below.

The apparatus stated in Patent Document 1 includes fuses in therespective phases of an inverter, and in an abnormal state where anyswitching element short-circuits, the apparatus prevents a brake torqueascribable to induced power in such a way that a current which is largerthan in an abnormal state is caused to flow through a short-circuitingpath, thereby to blow out the fuse and to open a closed circuit passingthrough the short-circuiting place.

Besides, an example of another prior-art apparatus is an apparatus whichis disclosed in Patent Document 2 indicated below.

The apparatus stated in Patent Document 2 is such that, in an abnormalstate where two phases short-circuit therebetween among the wires ofthree phases as connect a three-phase electric motor and switchingelements, motor relays disposed in the wires are held closed withoutbeing opened, thereby to continue controllable states. Besides, anyovercurrent is suppressed by limiting duties so that the upper switchingelements and lower switching elements of the two phases havingshort-circuited may not fall into their ON states at the same time.

-   Patent Document 1: JP-A-2003-81099-   Patent Document 2: JP-A-2005-153570

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

Heretofore, as an apparatus which continues a control in the abnormalstate of an electric motor or an inverter, there has been a controlscheme in an abnormal state where one phase falls into an open state, orin an abnormal state where two phases short-circuit therebetween.

However, there has not been an apparatus concerning a control scheme inwhich, in case of the occurrence of any other abnormal state, forexample, the grounding of one phase, the short-circuiting of the windingof one phase, or the short-circuiting of a switching element, a torqueoutput is continued without using a hardware device that is used in onlythe abnormal state.

In the example as stated in Patent Document 1, the fuse is blown out inthe abnormal state where the switching element short-circuits. Since,however, the hardware of the fuses needs to be added, the size and costof the inverter enlarge. Besides, although the brake torque ascribableto the induced power can be prevented, a control is not continued.

In the example as stated in Patent Document 2, in the abnormal statewhere the two phases short-circuit therebetween, the motor relays areheld closed, thereby to limit the duties of the abnormal phases.However, the apparatus merely continues the controllable state whilesuppressing the overcurrent, and it is not intended to suppress a torquepulsation ascribable to the abnormal state and to improve the operationof the motor, by contriving a current control method. Accordingly, theapparatus has the problem that the torque pulsation of the motorattributed to the abnormal state is large.

Besides, the prevention of the overcurrent in Patent Document 2 is basedon the limitation of the duties, and the switching elements are drivenin conformity with the duties which are really limited. Therefore, theapparatus has the problem that a short-circuiting path is formed due tothe errors of the response delays of a plurality of switching elementsor the error of the timing of the driving circuit of the switchingelements, so an overcurrent is apprehended to appear.

This invention has been made in view of the problems of the prior-artapparatuses as mentioned above, and it has for its object to provide acontrol apparatus for an electric motor, in which any overcurrent isprevented in a case where the abnormal state of the electric motor or aninverter has occurred, for example, where the grounding of one phase,the short-circuiting of the winding of one phase, the short-circuitingof any switching element, the short-circuiting between two phases, orthe like has occurred, and in which a current control method is alteredto a control scheme suited to the abnormal state, whereby a torquepulsation ascribable to the abnormal state is suppressed, and theoperation of the motor can be improved.

Means for Solving the Problems

An electric motor control apparatus according to this invention consistsin an electric motor control apparatus for a multiphase AC electricmotor, configured comprising a current detecting circuit which detectscurrents flowing through respective phases of the electric motor, acurrent control means for determining a multiphase voltage command inaccordance with a torque current command corresponding to a target valueof a torque to be generated by the electric motor and detection currentsof the respective phases from the current detecting circuit, a switchingelement driving circuit which commands an inverter to perform switchingmanipulations on the basis of the multiphase voltage command from thecurrent control means, and the inverter which consists of switchingelements that are operated by receiving switching manipulation signalsfrom the switching element driving circuit and that control currents tobe fed to the respective phases of the electric motor; wherein thecurrent control means further includes a normal-state currentcontrolling means for use in an normal state, an abnormal-state currentcontrolling means for use in an abnormal state, an abnormal-statedetermining means for determining the abnormal state of a wire of theelectric motor, a wire of the inverter, or a wire connecting theelectric motor and the inverter, and an abnormal phase disconnectingmeans; and wherein the abnormal phase disconnecting means disconnects atleast one of abnormal phases determined by the abnormal-statedetermining means, from the circuit, and the abnormal-state currentcontrolling means generates an abnormal-state voltage commandcorresponding to the abnormal state determined by the abnormal-statedetermining means, and uses phases other than the disconnected phase ofthe inverter so as to perform current controls of the phases with theabnormal-state voltage command used as the multiphase voltage command.

Besides, the electric motor control apparatus of this invention is soconfigured that an abnormal-state voltage command corresponding to theabnormal state determined by the abnormal-state determining means isgenerated by the abnormal-state current controlling means, and that boththe abnormal phase and normal phases of the inverter are used to performcurrent controls of the phases with the abnormal-state voltage commandused as the multiphase voltage command, without disconnecting theabnormal phase.

Advantages of the Invention

In accordance with the electric motor control apparatus of thisinvention, even in a case where an abnormal state such as grounding orshort-circuiting has occurred in the wire of an electric motor, the wireof an inverter, or a wire connecting the electric motor and theinverter, at least one of phases having undergone the abnormal states isdisconnected, thereby to prevent any overcurrent from flowing due to theabnormal state, and a control suited to the abnormal state can becontinued using the left phases of the inverter, to bring forth theadvantage that the torque output of the electric motor is continued andthat a torque pulsation ascribable to the abnormal state is suppressed,so the operation of the motor can be improved.

Besides, in accordance with the electric motor control apparatus of thisinvention, in a case where a short-circuiting abnormal state hasoccurred in one phase of the wire of an electric motor, the wire of aninverter, or a wire connecting the electric motor and the inverter, avoltage command suited to the abnormal state is generated using both theabnormal phase and normal phases of the inverter, whereby the torqueoutput of the electric motor is continued, and a torque pulsationascribable to the abnormal state is suppressed, so that the operation ofthe motor can be improved.

Furthermore, in accordance with the electric motor control apparatus ofthis invention, it is possible to obtain a control apparatus for anelectric motor as is suitable as a control apparatus for a three-phasebrushless motor which is used for driving an electrically-driven powersteering apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing the whole configuration ofan electric motor control apparatus according to Embodiment 1 of thepresent invention.

FIG. 2 is a block diagram showing the configuration of a current controlmeans in Embodiment 1 of the invention.

FIG. 3 is a control block-line diagram of an abnormal-state currentcontrolling means in Embodiment 1 of the invention.

FIG. 4 is a block diagram showing an example of the configuration of aphase current command shaping means in Embodiment 1 of the invention.

FIG. 5 is a diagram showing examples of untarget phase currents and amotor torque waveform in Embodiment 1 of the invention.

FIG. 6 is a diagram showing examples of current waveforms and a braketorque in the abnormal state where one phase grounds in the electricmotor control apparatus.

FIG. 7 is a diagram of a motor torque waveform in the abnormal statewhere one phase grounds in case of employing a control in the prior art.

FIG. 8 is a diagram of a motor torque waveform in the abnormal statewhere one phase grounds in case of employing the electric motor controlapparatus according to Embodiment 1 of the invention.

FIG. 9 is a control block-line diagram of an abnormal-state currentcontrolling means in Embodiment 2 of the invention.

FIG. 10 is a control block-line diagram of an abnormal-state currentcontrolling means in Embodiment 3 of the invention.

FIG. 11 is a control block-line diagram of an abnormal-state currentcontrolling means in Embodiment 4 of the invention.

FIG. 12 is a diagram showing examples of a untarget phase current and amotor torque waveform in Embodiment 4 of the invention.

FIG. 13 is a diagram of a motor torque waveform in the abnormal statewhere two phases short-circuit therebetween in case of employing acontrol in the prior art.

FIG. 14 is a diagram of a motor torque waveform in the abnormal statewhere two phases short-circuit therebetween in case of employing anelectric motor control apparatus according to Embodiment 4 of theinvention.

FIG. 15 is a block diagram showing the configuration of a currentcontrol means in Embodiment 5 of the invention.

FIG. 16 is a control block-line diagram of an abnormal-state currentcontrolling means in Embodiment 5 of the invention.

FIG. 17 is a diagram showing examples of untarget phase currents andmotor torque waveforms in Embodiment 5 of the invention.

FIG. 18 is a diagram of a motor torque waveform in the abnormal statewhere one phase short-circuits in case of employing the control in theprior art.

FIG. 19 is a diagram of a motor torque waveform in the abnormal statewhere one phase short-circuits in case of employing an electric motorcontrol apparatus according to Embodiment 5 of the invention.

FIG. 20 is a control block-line diagram of the abnormal-state currentcontrolling means in the invention.

FIG. 21 is a schematic configurational diagram of an electrically-drivenpower steering apparatus according to Embodiment 8 of the invention.

FIG. 22 is a block diagram showing the configuration of a controllerunit in Embodiment 8 of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

Embodiment 1 of this invention will be described in conjunction with thedrawings.

Incidentally, although a case where this invention is applied to athree-phase brushless motor will be exemplified in the ensuingdescription, this invention is not limited thereto, but it can be usedfor an electric motor which is driven to rotate by a multiphasealternating current.

FIG. 1 is a schematic block diagram showing the whole configuration ofan electric motor control apparatus according to Embodiment 1 of thisinvention.

Referring to FIG. 1, numeral 10 designates the electric motor controlapparatus, and the brushless motor (hereinbelow, also termed “motor”) 5which includes the windings of the three phases of U-, V- and W-phasesis controlled by employing this electric motor control apparatus 10.

The electric motor control apparatus 10 receives a signal from a motorangle sensor 6 which detects the rotation angle of the motor 5, and itcalculates the rotation angle of the motor by a motor rotation angledetecting circuit 21. Besides, the electric motor control apparatuscalculates currents flowing through the respective phases of the motor5, by a current detecting circuit 22.

As will be stated later, a current control means 23 determines athree-phase voltage command in accordance with a torque current commandcorresponding to the target value of a motor torque, the detectioncurrents of the respective motor phases, and the motor rotation angle. Aswitching element driving circuit 24 subjects the three-phase voltagecommand determined by the current control means 23, to PWM modulation,and thus commands an inverter 25 to perform switching manipulations.

The inverter 25 receives switching manipulation signals from theswitching element driving circuit 24, thereby to realize the choppercontrols of switching elements 61A-63A and 61B-63B constituting outputarms, and it causes currents to flow through the respective phases ofthe motor 5, by electric power fed from a battery 11. The motor torqueis generated by the currents flowing through the respective phases.

Next, the current control means 23 will be described with reference to ablock diagram of FIG. 2.

As shown in FIG. 2, the current control means 23 includes a normal-statecurrent controlling means 31 for executing an ordinary control schemefor use in a normal state, an abnormal-state current controlling means30 for use in an abnormal state, an abnormal-state determining means 32,a switching means 33, and an abnormal phase disconnecting means 34, andit is permitted to switch the two current controlling means 30 and 31.

The abnormal-state determining means 32 performs the followingdetermination on the basis of the three-phase detection currents fedfrom the current detecting circuit 22. That is, when the length of atime, for which the magnitude of the detection current of any phaseremains above a preset value and for which the detection currents of theother phases remain at or below the preset value, has reached a presetvalue, the abnormal-state determining means 32 determines that the phaseis in an abnormal state. With such an abnormal-state determining means,abnormal states are not determined independently of the respectivephases, but they are determined relatively or comprehensively on thebasis of the detection currents of the three phases, so that theapprehension of an erroneous determination can be relieved.

Besides, the abnormal-state determining means 32 feeds an abnormal-statedetermination signal to the abnormal-state current controlling means 30,the switching means 33 and the abnormal phase disconnecting means 34 inorder to notify the presence or absence of any abnormal state and theabnormal phase.

The abnormal-state current controlling means 30 receives theabnormal-state determination signal from the abnormal-state determiningmeans 32, and it stops its function in a normal state, whereas itperforms a control coping with any abnormal phase in a case where theabnormal state has been detected from the certain phase.

The switching means 33 receives the abnormal-state determination signalfrom the abnormal-state determining means 32, and it outputs athree-phase normal-state voltage command from the normal-state currentcontrolling means 31 as the three-phase voltage command in a case wherethe signal of the normal state has been detected, whereas it outputs athree-phase abnormal-state voltage command from the abnormal-statecurrent controlling means 30 as the three-phase voltage command in acase where the signal of the abnormal state has been detected.

The abnormal phase disconnecting means 34 receives the abnormal-statedetermination signal from the abnormal-state determining means 32, andit sends a command for stopping the drive of the switching element ofthe abnormal phase, to the switching element driving circuit 24 in orderto disconnect the abnormal phase for the purpose of preventing anyovercurrent.

Incidentally, the normal-state current controlling means 31 may beconfigured of a known device as shown in, for example, FIG. 17 ofInternational Publication WO 2005/091488, and it performs an ordinary dqcontrol in the normal state, thereby to realize the generation of asmooth motor torque. Since it is not directly pertinent to the purportof this invention, it shall be omitted from detailed description.

Next, there will be described a case where an abnormal state hasoccurred in one phase of the motor or the inverter, for example, a casewhere an abnormal state in which the V-phase of motor wiring, theV-phase of inverter wiring, or the V-phase of wiring connecting themotor and the inverter short-circuits to a wire leading to the minuspotential of the battery, or an abnormal state in which the lowerswitching element of one phase, for example, the V-phase of the outputarms of the inverter short-circuits, that is, the grounding of one phasehas developed.

In the case where such an abnormal state has developed, theabnormal-state determining means 32 feeds the abnormal-statedetermination signal signifying “that the V-phase is abnormal”, to theabnormal-state current controlling means 30, the switching means 33 andthe abnormal phase disconnecting phase 34 in FIG. 2. In order to preventany overcurrent from appearing in the V-phase which has undergone theabnormal state, the abnormal phase disconnecting means 34 sends theswitching element driving circuit 24 a command for stopping the drivesof the switching elements 62A and 62B of the V-phase. Owing to theswitching element driving circuit 24 which has received this command,the V-phase switching elements 62A and 62B continue their disabledstates, and a drive stop state is established therefor.

Besides, owing to the abnormal-state determination signal, theabnormal-state current controlling means 30 is actuated, and thethree-phase abnormal-state voltage command is fed to the switchingelement driving circuit 24 as the three-phase voltage command throughthe switching means 33. The abnormal-state current controlling means 30executes a control scheme shown in FIG. 3, in order to perform a currentcontrol in which the phase having undergone the abnormal state isconsidered.

Now, the control operation of the abnormal-state current controllingmeans 30 will be described with reference to FIGS. 3 and 4. FIG. 3 is acontrol block-line diagram of the abnormal-state current controllingmeans 30 a in the foregoing case where the V-phase has grounded, andthis control scheme shall be called the “grounding-state three-phaseindividual control” below.

Referring to FIG. 3, a phase current command shaping means 50 generatesthe phase current commands of the respective phases in accordance withthe torque current command, the motor rotation angle, and a motorrotation angular velocity obtained by approximately differentiating themotor rotation angle by a differentiating means 51. Subtractors 44, 45and 46 calculate the current deviations of the corresponding phases,respectively, in such a way that the U-, V- and W-phase detectioncurrents obtained by the current detection circuit 22 are subtractedfrom U-, V- and W-phase current commands. Subsequently, in order tocarry out the current controls of the respective phases with referenceto the phase having grounded, subtractors 72 and 73 subtract the currentdeviation of the V-phase having undergone the abnormal state, from thecurrent deviations of the normal U- and W-phases, and they feed theresulting differences to a U-phase controller 41 and a W-phasecontroller 43 which are formed of PI controls or the likes.

In order to offset the voltage commands of the normal phases to thevoltage of the phase having grounded into the battery minus voltage andto make them appropriate commands, adders 74 and 75 add the batteryminus voltage value VN of a minus voltage circuit 54 to U- and W-phasecommands outputted from the U-phase controller 41 and the W-phasecontroller 43, thereby to generate the U- and W-phase voltage commands.The “battery minus voltage value” termed here is a value obtained bybringing the value of ½ of a battery voltage VB into a minus value, thatis, VN=−VB/2 holds.

In this way, the abnormal-state controlling means 30 a shown in FIG. 3controls the normal phases individually in accordance with the groundingwhich has developed in the V-phase.

The phase current command shaping means 50 has a configuration as shownin FIG. 4 by way of example.

A unit phase current command generating means 501 determines the unitphase current commands of the respective phases in accordance with thetorque current command, the motor rotation angle and the motor rotationangular velocity.

Multiplication means 502U, 502V and 502W multiply the torque currentcommand and the unit phase current commands of the corresponding phases,respectively, thereby to calculate the phase current commands of therespective phases. The unit phase current commands signify the phasecurrent commands of the respective phases at the time when the magnitudeof the torque current command is “1”.

In the unit phase current command generating means 501, the relations ofthe unit phase current commands to the torque current command, the motorrotation angle and the motor rotation angular velocity are, for example,relations shown in FIG. 5.

When the unit phase current commands are generated by employing therelations of FIG. 5( a) and such phase current commands can be realizedas the currents of the respective phase windings, a motor torquewaveform as shown in FIG. 5( b) can be obtained. This is a command whichis intended to output a torque of plus direction being as flat aspossible, in the abnormal state where one phase grounds as statedbefore. The motor rotation angle on the axis of abscissas is on thescale of the electrical angle of the motor.

Incidentally, the motor rotation angular velocity is not used in thecalculation of the unit target phase currents, and an example which usesthe motor rotation angular velocity will be described in Embodiment 6later.

Besides, the abnormal-state current controlling means 30 a is providedwith the selective switching element disabling means 53, and theswitching element driving circuit 24 can be commanded to temporarilydisable the switching elements of the normal phases, in accordance withthe motor rotation angle.

By way of example, in the case of employing the unit phase currentcommands shown in FIG. 5( a), the U-phase switching elements 61A and 61Band the W-phase switching elements 63A and 63B are disabled at the motorrotation angle (0-60°) at which currents are to be zeroized, whereby thenumber of current paths can be decreased.

Incidentally, FIG. 3 shows the control block-line diagram of thegrounding-state three-phase individual control in the case where theabnormal state has occurred in the V-phase, but even in cases whereabnormal states have developed in the U- and W-phases, similargrounding-state three-phase individual controls are included in theabnormal-state current controlling means 30 a, and they can be switcheddepending upon the phases in which the abnormal states have occurred.

Here, in order to indicate the advantages of this invention, problems inthe abnormal state where one phase grounds as stated before will bestated below.

In the abnormal state where one phase grounds as stated before, a closedcircuit passing through a grounding place is formed, and hence, a motorrotation angle at which the appearance of a brake torque ascribable tothe induced power of the motor is inevitable is existent. The braketorque is a torque which acts in the direction of hampering the rotationof the motor. Even in a case where all the switching elements aredisabled, the closed circuit is maintained through the diodes of thenormal phases, so that currents based on the induced power flow as shownin FIG. 6, and the brake torque appears.

Incidentally, the diodes are usually included in parallel with therespective switching elements within the inverter 25 as shown in FIG. 1.

Referring to FIG. 5, the unit phase current commands and the motortorque waveform are zeroized at the motor rotation angle (0-60°). Themotor rotation angle is a region in which the appearance of the braketorque cannot be prevented, and it is intended to make the currentssmall even slightly and to make the brake torque small.

Originally, in order to output the plus torque, the voltage of theV-phase ought to be made the highest in the angular region. However, nowthat the voltage is the lowest value, namely, the minus voltage of thebattery on account of the grounding of the V-phase, the generation ofthe plus torque is impossible. Further, since the closed circuit passingthrough the grounding place is existent, the brake torque appears, andit is difficult to prevent this brake torque.

Besides, when the control is performed by employing the control schemewhich is used in the normal state, for example, the dq control, in theabnormal state where one phase grounds as stated before, it is notsuited to the abnormal state. As shown in FIG. 7, therefore, there arethe problems that the part of a minus value, namely, the brake torque islarge, and that also a torque pulsation becomes large.

In contrast, when the grounding-state three-phase individual control inEmbodiment 1 of this invention is used, the current commands of therespective phases suitable for the abnormal state are generated by thephase current command shaping means 50, and the control is configured soas to realize the current commands. As in a motor torque waveform shownin FIG. 8, therefore, the appearance of the brake torque is suppressedto the utmost, and the torque pulsation can be made small.

Besides, the number of current paths is decreased in the region wherethe appearance of the brake torque is inevitable, by the selectiveswitching element disabling means 53, so that the brake torque can beminimized.

Besides, in a case where the abnormal-state determining means 32determines any abnormal state, depending upon the magnitudes ofdetection currents independently of the respective phases, thedetermination of the abnormal state is apprehended to be erroneouslydone under the influence of noise or the abnormal state of any otherphase when, by way of example, the current is controlled to a largecurrent value near the threshold value of determination.

With the abnormal-state determining means stated in Embodiment 1,however, the abnormal state is determined, not only by estimating thevalues of the detection currents of the respective phases in terms ofthe respective absolute values thereof, but also by estimating thevalues of the detection currents of the three phases relatively, so thatthe apprehension of the erroneous determination can be relieved.

As described above, according to the control apparatus of Embodiment 1of this invention, even in the case where the abnormal state hasoccurred in the wire of the electric motor, the wire of the inverter, orthe wire connecting the electric motor and the inverter, and where theovercurrent is apprehended to appear due to the abnormal state, thephase having undergone the abnormal state is disconnected by theabnormal phase disconnecting means 34, and further, using the phaseswhich remain without being disconnected, the current control iscontinued by the abnormal-state current controlling means 30 replacingthe normal-state current controlling means 31, and the respective phasescan be individually controlled on the basis of the current commands andvoltage commands corresponding to the abnormal state.

Accordingly, the overcurrent is prevented, whereupon the torque outputof the electric motor is continued, and the torque pulsation ascribableto the abnormal state is suppressed, so that the operation of the motorcan be improved.

Embodiment 2

FIG. 9 is a control block-line diagram of an abnormal-state currentcontrolling means 30 b according to Embodiment 2 of this invention.

In the abnormal-state current controlling means 30 a of thegrounding-state three-phase individual control of Embodiment 1 as shownin FIG. 3, the phase current command is generated also for the V-phasehaving undergone the abnormal state, and the control is performed byemploying also the V-phase detection current. In contrast, in Embodiment2, as shown in FIG. 9, the phase current command shaping means 50generates only U- and W-phase current commands, U- and W-phase detectioncurrents are respectively subtracted from the U- and W-phase currentcommands by the subtractors 44 and 46, and the resulting currentdeviations are fed to the U-phase controller 44 and W-phase controller46, so as to individually control the respective phases.

Also with the configuration of FIG. 9, a control which is substantiallyequivalent to the grounding-state three-phase individual control ofEmbodiment 1 is possible, and the same advantages as those of thegrounding-state three-phase individual control can be attained in thegrounding state of the V-phase.

Embodiment 3

FIG. 10 is a control block-line diagram of an abnormal-state currentcontrolling means 30 c according to Embodiment 3 of this invention.

In Embodiment 1, the grounding-state three-phase individual control inFIG. 3 has been employed as the abnormal-state current controllingmeans, but a similar control is possible even when a control system ondq coordinates is employed. One aspect of the control system will now bedescribed as Embodiment 3.

As the abnormal-state current controlling means, the abnormal-statecurrent controlling means 30 c shown in FIG. 10 is executed instead ofthe grounding-state three-phase individual control in FIG. 3 as employedin Embodiment 1.

The control scheme shown in FIG. 10 is substantially similar to the dqcontrol which is employed in the normal state, but it features that theintegral terms of d- and q-axis controllers are limited.

Now, FIG. 10 will be described in detail.

A dq-axis current command shaping means 80 generates d- and q-axiscurrent commands in accordance with a torque current command and a motorrotation angle. Subsequently, d-axis and q-axis detection currentsoutputted from a two-phase conversion means 86 are respectivelysubtracted from the d-axis and q-axis current commands by subtractors 83and 84, thereby to calculate d-axis and q-axis current deviations, whichare respectively fed to the d-axis controller 81 and the q-axiscontroller 82. In the respective d- and q-axis current controllers 81and 82, there are proportional terms which multiply the d- and q-axiscurrent deviations by proportional gains 111 d and 111 q, and integralterms which multiply the d- and q-axis current deviations integrated byintegrators 113 d and 113 q, by integral gains 112 d and 112 q. Resultscalculated here are respectively added, thereby to generate d- andq-axis voltage commands. The integral terms include integral termlimitation means 114 d and 114 q at their output parts, and the valuesof the integral terms can be limited to values smaller than in thenormal state.

Incidentally, although the aspect in which the integral term outputs arelimited by the integral term limitation means 114 d and 114 q isillustrated here, the limitations are similarly attained even when theintegral gains 112 d and 112 q of the integral terms are limited tosmaller values. Besides, the integral terms may well be zeroized.

A three-phase conversion means 85 subjects the d- and q-axis voltagecommands to three-phase conversion in accordance with the motor rotationangle, thereby to generate U-, V- and W-phase voltage commands.

Besides, although the torque current command has been shaped inaccordance with the motor rotation angle by the dq-axis current commandshaping means 80, the q-axis current command may well be generatedwithout shaping the torque current command, without employing thedq-axis current command shaping means.

In this manner, the integral terms are limited, and the q-axis currentcommand is shaped by the dq-axis current command shaping means in somecases, whereby the abnormal-state current controlling means can beconfigured though the dq control is basically employed.

Besides, although the example as shown in FIG. 10 has been illustratedin Embodiment 3, the abnormal-state current controlling means whichemploys the control system on the dq coordinates can also be in anotheraspect owing to a modification based on the linearity of a controlblock.

With the control apparatus in Embodiment 3 of this invention, theintegral terms are limited to smaller values than in a normal state, andthe d- and q-axis current commands are shaped by the dq-axis currentcommand shaping means 80, whereby the appearance of a brake torque canbe suppressed more, and a torque pulsation can be made smaller, than ina case where the dq control in the normal state is continued as it is.

Incidentally, although the abnormal state where one phase grounds hasbeen stated in the above embodiments, a similar control is possible, andsimilar advantages are attained, by making a slight modification also inan abnormal state where one phase shorts-out to a power supply, that is,an abnormal state where one of a motor wire, an inverter wire and a wireconnecting the motor and the inverter short-circuits to a wire leadingto the plus potential of the battery, or an abnormal state where theupper switching element of one phase of the inverter short-circuits.

Embodiment 4

Embodiment 1 concerns the case of the occurrence of an abnormal statewhere one of a motor wire, an inverter wire and a wire connecting themotor and the inverter, in the V-phase, short-circuits to a wire leadingto the minus potential of the battery, or an abnormal state where thelower switching element of the V-phase of the inverter short-circuits,that is, the grounding of one phase, and the abnormal-state currentcontrolling means which corresponds to the abnormal state has beendescribed. In Embodiment 4, there will be described a case where anabnormal state in which two phases short-circuit therebetween, in otherwords, interphase short-circuiting has occurred.

The ensuing description will mention, for example, an abnormal statewhere one of a motor wire, an inverter wire and a wire connecting themotor and the inverter, in the U-phase, short-circuits to one of themotor wire, the inverter wire and the wire connecting the motor and theinverter, in the V-phase, that is, UV-phase short-circuiting.

In a case where such an abnormal state has occurred, the abnormal-statedetermining means 32 feeds an abnormal-state determination signalsignifying “that the U-phase and the V-phase are abnormal”, to theabnormal-state current controlling means 30, the switching means 33 andthe abnormal phase disconnecting means 34 in FIG. 2.

In order to prevent an overcurrent from being generated through theU-phase and the V-phase which have undergone the interphaseshort-circuiting, the abnormal phase disconnecting means 34 sends theswitching element driving circuit 24 a command for stopping the drivesof the switching elements 61A and 61B of the U-phase. Owing to theswitching element driving circuit 24 having received the command, theU-phase switching elements 61A and 61B continue their OFF states, and adrive stop state is established therefor. Either the U-phase or theV-phase may have its drive stopped, and the U-phase is brought into thedrive stop state here.

Besides, the abnormal-state current controlling means 30 is actuated bythe abnormal-state determination signal, and a three-phaseabnormal-state voltage command is fed to the switching element drivingcircuit 24 through the switching means 33 as a three-phase voltagecommand. The abnormal-state current controlling means 30 executes acontrol scheme shown in FIG. 11, in order to perform a current controlin which the phases having undergone the abnormal states are considered.

Now, the control operation of the abnormal-state current controllingmeans 30 will be described in conjunction with FIGS. 11 and 4.

FIG. 11 is a control block-line diagram of the abnormal-state currentcontrolling means 30 d in the case where the U-phase switching elementshave been brought into the drive stop states at the occurrence of theUV-phase short-circuiting, and this control scheme shall be called the“UV-phase short-circuiting-state three-phase individual control” below.

The configuration of a phase current command shaping means 50 in FIG. 11is similar to that of the means 50 in FIG. 4, but it may be aconfiguration which outputs only a W-phase current command. Therelations of the unit phase current command to a torque current command,a motor rotation angle and a motor rotation angular velocity in a unitphase current command generating means 501 are, for example, relationsshown in FIG. 12.

Motor rotation angles at which a motor torque becomes zero or can begenerated in only a reverse direction, are existent in the two-phaseshort-circuiting state. They are 60 degrees and 240 degrees in FIG. 12.In the vicinities of the angles, larger currents than in any otherangular region are necessitated for generating torques in a forwarddirection. In the vicinity of each angle, therefore, the phase currentcommand is enlarged to enlarge a phase voltage command, whereby thelarger current is caused to flow.

Thus, a torque as shown in FIG. 12( b) can be generated in the normalW-phase.

Besides, in order to suppress a brake torque which enlarges inproportion to the motor rotation angular velocity, the unit phasecurrent command may well be enlarged in proportion to the motor rotationangular velocity.

In this manner, in the case where the interphase short-circuiting hasoccurred, a current control is continued by an abnormal-state currentcontrolling means replacing a normal-state current controlling means,whereby the respective phases can be individually controlled by thecurrent command and the voltage command which correspond to the abnormalstate.

Here, in order to indicate the advantages of Embodiment 4 of thisinvention, problems in the abnormal state where the phases short-circuittherebetween will be stated below.

In the abnormal state where the phases short-circuit therebetween asstated before, a closed circuit which passes through the motor windingsof the two phases having short-circuited with a short-circuiting placeis formed, and hence, the motor rotation angle at which the appearanceof the brake torque ascribable to the induced power of the motor isinevitable is existent. The brake torque is a torque which acts in thedirection of hampering the rotation of the motor.

Even in a case where the motor rotation angular velocity is zero andwhere the induced power does not act, the motor rotation angle at whichthe motor torque becomes zero is existent. In the vicinity of the angle,the induced power between the two short-circuiting phases is especiallylarge, and the current needs to be enlarged for the purpose of cancelingthe brake torque ascribable to the induced power. Since, however, thecurrent which can be caused to flow has an upper limit ordinarily, it isdifficult to suppress the appearance of the brake torque.

Besides, when the control is performed by employing the control schemewhich is used in the normal state, for example, the dq control, in theabnormal state where the interphase short-circuiting occurs as statedbefore, it is not suited to the abnormal state. As shown in FIG. 13,therefore, there are the problems that the region of a minus value,namely, the region of the brake torque is large, and that also a torquepulsation becomes large.

In contrast, when the control apparatus in Embodiment 4 of thisinvention is used, the current commands of the respective phasessuitable for the abnormal state are generated by the phase currentcommand shaping means 50, and the control is configured so as to realizethe current commands, and hence, the torque based on the normal phasecan be enlarged in the vicinity of the motor rotation angle at which themotor torque becomes zero. As in a motor torque waveform shown in FIG.14, therefore, the appearance of the brake torque is suppressed to theutmost, and the torque pulsation can be made small.

Besides, in the abnormal state where the interphase short-circuitingoccurs, an overcurrent is apprehended to appear through theshort-circuiting place and the U-phase and V-phase switching elements.However, according to the control apparatus in Embodiment 4 of thisinvention, the switching elements of either of the two phases in whichthe abnormal states have been detected can be brought into the drivestop states by the abnormal phase disconnecting means, so that theovercurrent can be prevented.

Embodiment 5

In Embodiment 5, there will be described a case where an abnormal statein which one phase of a motor winding short-circuits, that is, one-phaseshort-circuiting has occurred. By way of example, a case where anabnormal state in which the winding of the U-phase short-circuits, thatis, U-phase short-circuiting has occurred will be described below.

FIG. 15 is a block diagram showing the configuration of a currentcontrol means 23 a in Embodiment 5 of this invention.

In a case where such an abnormal state has occurred, the abnormal-statedetermining means 32 feeds an abnormal-state determination signalsignifying “that the U-phase is abnormal”, to the abnormal-state currentcontrolling means 30 and the switching means 33 in FIG. 15.

The abnormal-state current controlling means 30 is actuated by theabnormal-state determination signal, and a three-phase abnormal-statevoltage command is fed to the switching element driving circuit 24through the switching means 33 as a three-phase voltage command.

The abnormal-state current controlling means 30 executes a controlscheme shown in FIG. 16, in order to perform a current control in whichthe phase having undergone the abnormal state is considered.

Now, the control operation of the abnormal-state current controllingmeans 30 will be described in conjunction with FIGS. 16 and 4.

FIG. 16 is a control block-line diagram of the abnormal-state currentcontrolling means 30 e in the case where the U-phase switching elementshave been brought into the drive stop states at the occurrence of theU-phase short-circuiting, and this control scheme shall be called the“U-phase short-circuiting-state three-phase individual control” below.

Referring to FIG. 16, the phase current command shaping means 50generates V- and W-phase current commands in accordance with a torquecurrent command, a motor rotation angle, and a motor rotation angularvelocity. Subtractors 45 and 46 calculate the current deviations of thecorresponding phases, respectively, in such a way that V- and W-phasedetection currents obtained by the current detection circuit 22 aresubtracted from the V- and W-phase current commands, and they feed theresulting current deviations to a V-phase controller 42 and a W-phasecontroller 43 which are formed of PI controls or the likes. The V- andW-phase controllers 42 and 43 output V- and W-phase voltage commands,respectively. In the state of the U-phase short-circuiting, a currentwhich can be detected by a U-phase current detecting circuit is thetotal of currents flowing through a short-circuiting place and a U-phasewinding, and a current flowing through the U-phase winding cannot bedetected, so that a controller need not be disposed for the U-phasecurrent. Regarding a U-phase voltage command, however, the V- andW-phase voltage commands have their signs changed and are then added bya subtractor 76, and the resulting sum is outputted as the U-phasevoltage command, in order to control the V- and W-phases at good voltageefficiencies.

In this way, the abnormal-state controlling means 30 e shown in FIG. 16performs the controls individually for the normal phases in accordancewith the abnormal state of the U-phase short-circuiting.

The phase current command shaping means 50 has the configuration inEmbodiment 1 as shown in FIG. 4 by way of example. In Embodiment 5,however, the U-phase current command is unnecessary.

In the unit phase current command generating means 501, the relations ofthe unit phase current commands to the torque current command, the motorrotation angle and the motor rotation angular velocity are, for example,relations shown in FIG. 17.

When the V- and W-phase unit phase current commands are generated byemploying the relations of FIG. 17( a) and such phase current commandscan be realized as the currents of the respective phase windings, amotor torque waveform as shown in FIG. 17( b) can be obtained in theabsence of any induced power.

The current commands in FIG. 17( a) assume large values near motorrotation angles of 60 degrees to 120 degrees and near ones of 240degrees to 300 degrees. The vicinities of the angular regions areregions where the induced powers of the U-phase having short-circuitedenlarge, and in order to suppress the influences of brake torquecomponents appearing in the U-phase, the current commands are intendedto enlarge the currents of the normal V- and W-phases and to enlargeforward-direction torque components based on the V- and W-phases.

The motor rotation angle on the axis of abscissas is on the scale of theelectrical angle of the motor.

Here, in order to indicate the advantages of Embodiment 5 of thisinvention, problems in the abnormal state where the phase short-circuitswill be stated below.

In the abnormal state where one phase short-circuits as stated before, aclosed circuit which passes through a short-circuiting place and thewinding having short-circuited is formed, and hence, the motor rotationangle at which the appearance of the brake torque ascribable to theinduced power of the motor is inevitable is existent. The brake torqueis a torque which acts in the direction of hampering the rotation of themotor.

When the control is performed by employing the dq control which is usedin the normal state, in the abnormal state where one phaseshort-circuits as stated before, it is not suited to the abnormal state.As shown in FIG. 18, therefore, there are the problems that the braketorque is large, and that also a torque pulsation becomes large.

In contrast, when the control apparatus in Embodiment 5 of thisinvention is used, the current commands of the respective phasessuitable for the abnormal state are generated by the phase currentcommand shaping means 50, and the control is configured so as to realizethe current commands. As in a motor torque waveform shown in FIG. 19,therefore, the appearance of the brake torque is suppressed to theutmost, and the torque pulsation can be made small.

Embodiment 6

Although, in the unit phase current command generating means 501 inEmbodiments 1-5, the relation shown in FIG. 5 has been applied to therelation of the unit phase current command to the motor rotation angle,the command value may well be further changed in accordance with themotor rotation angular velocity. By way of example, the unit phasecurrent command in FIG. 5 is increased in proportion to the increase ofthe motor rotation angular velocity.

In the angular region where the appearance of the brake torque isinevitable, the brake torque enlarges in proportion to the motorrotation angular velocity, and hence, the motor torque is enlarged inthe angular region where the torque in the plus direction is possible,by the unit phase current command in this embodiment, whereby a motoroutput can be ensured on the average. Therefore, the motor output can bemade less prone to become insufficient.

Embodiment 7

Regarding the control block-line diagrams of the abnormal-state currentcontrolling means described in the foregoing embodiments, modificationsbased on the linearities of the constituents are respectively possible,and even when the modifications based on the linearities are made,controls equivalent to those before the modifications can be performed,and hence, equivalent advantages can be obtained.

FIG. 20 is a control block-line diagram of an abnormal-state currentcontrolling means 30 f in Embodiment 7 of this invention, in which theabnormal-state current controlling means 30 a shown in FIG. 3 has beenmodified on the basis of such a linearity.

In FIG. 20, the same reference numerals as in FIG. 3 indicate identicalor equivalent parts.

FIG. 20 has been modified so as to become equivalent to FIG. 3, owing tothe property of linear elements that, in a case where the U-phasecontroller 41 and the V-phase controller 42 in FIG. 3 are linear and thesame, additions/subtractions at the inputs of the elements arerespectively equivalent to additions/subtractions at the outputs thereofafter the computations.

Incidentally, although the case of the three-phase motor has beenchiefly stated in the above embodiments 1-7, it is needless to say thatthe invention is similarly applicable to a motor of four or more phasesand that similar advantages are obtained, by designating target phasecurrents individually for the respective phases and disposingcontrollers individually.

Embodiment 8

FIGS. 21 and 22 show Embodiment 8 of this invention, and they show anexample in which the electric motor control apparatus of this inventionas illustrated in any of the foregoing embodiments is applied to anelectrically-driven power steering apparatus. Incidentally, there willbe exemplified a case where the electrically-driven power steeringapparatus includes a three-phase brushless motor, but this invention canbe used also for any other apparatus whose power is generated by anelectric motor that is driven to rotate by a multiphase alternatingcurrent.

FIG. 21 is a schematic configurational diagram of theelectrically-driven power steering apparatus according to Embodiment 8of this invention. Referring to FIG. 21, a steering force exerted on asteering wheel 1 by a driver not shown is passed through a steeringshaft 2 and is transmitted to a rack through a rack-and-pinion gear 12,thereby to steer wheels 3 and 4. The brushless motor 5 (hereinbelow,also termed the “motor”) including the windings of the three-phases ofU-, V- and W-phases is connected with the steering shaft 2 through amotor reduction gear 7. A motor torque (hereinbelow, also termed the“assisting force”) generated by the motor is transmitted to the steeringshaft 2 through the motor reduction gear 7, and it relieves the steeringforce which the driver exerts in a steering operation.

A torque sensor 8 detects the steering force exerted on the steeringshaft 2 in such a way that the driver steers the steering wheel 1. Acontroller unit 9 determines the direction and magnitude of theassisting force which the motor 5 is to bestow, in accordance with thesteering force detected by the torque sensor 8, and it controls currentswhich are to flow from a power source 11 to the motor, in order togenerate the assisting force. Incidentally, numeral 6 designates a motorangle sensor which detects the rotation angle of the motor.

FIG. 22 is a block diagram showing the configuration of the controllerunit 9.

Referring to FIG. 22, the controller unit 9 is configured of a map 20which calculates a torque current command corresponding to the targetvalue of a motor torque, and an electric motor control apparatus 10.

The map 20 in which motor torques to be outputted are stored beforehand,determines the direction and magnitude of the motor torque correspondingto the steering force detected by the torque sensor 8 and calculates thetorque current command. In order to realize the torque current command,the electric motor control apparatus 10 controls the currents flowingthrough the respective phases of the motor. The assisting force based onthe motor 5 is generated by the currents.

The electric motor control apparatus 10 is, for example, one shown inany of Embodiments 1-3.

Here will be described problems in the abnormal state where one phase inthe electrically-driven power steering apparatus grounds.

As stated also in Embodiment 1, in the abnormal state where one phasegrounds, a closed circuit passing through a grounding place is formed,and hence, a motor rotation angle at which the appearance of a braketorque ascribable to the induced power of the motor is inevitable isexistent. The brake torque is a torque which acts in the direction ofhampering the rotation of the motor. Besides, when a control is executedby employing a dq control which is used in a normal state, in theabnormal state of the grounding of one phase, it is not suited to theabnormal state. Therefore, there are the problems that the brake torqueis large, and that a torque pulsation becomes large in plus and minusdirections.

In case of an electrically-driven power steering apparatus, accordingly,a sense of incompatibility which the driver feels is intense.

On the other hand, according to the electrically-driven power steeringapparatus configured as stated above, in the case of the abnormal statewhere one phase grounds, the appearance of the brake torque issuppressed to the utmost, and the torque pulsation can be made small.Besides, in a region where the appearance of the brake torque isinevitable, the brake torque can be minimized by a selective switchingelement disabling means. Therefore, the sense of incompatibility whichthe driver feels can be relieved.

Incidentally, the electric motor control apparatus stated above has beenone illustrated in any of Embodiments 1-3, but the electric motorcontrol apparatus illustrated in Embodiment 4 may well be employed. Acase where the abnormal state of the interphase short-circuiting betweentwo phases has occurred, will be stated below.

Besides, there will be described problems in the abnormal state wherethe two phases in the electrically-driven power steering apparatusundergo the interphase short-circuiting.

In the abnormal state of the interphase short-circuiting, a closedcircuit is formed through a short-circuiting place and the motorwindings of the two phases having short-circuited, and hence, a motorrotation angle at which the appearance of a brake torque ascribable tothe induced power of the motor is inevitable is existent. The braketorque is a torque which acts in the direction of hampering the rotationof the motor. Even in a case where the rotation angular velocity of themotor is zero and where the induced power does not act, a motor rotationangle at which a motor torque becomes zero is existent. In the vicinityof the angle, the induced power between the two short-circuiting phasesis especially large, and a current needs to be enlarged for the purposeof canceling the brake torque ascribable to the induced power. Since,however, the current which can be caused to flow has an upper limitordinarily, it is difficult to suppress the appearance of the braketorque.

Besides, when the control is performed by employing the dq control whichis used in the normal state, in the abnormal state of the interphaseshort-circuiting, it is not suited to the abnormal state. Therefore,there are the problems that the brake torque is large, and that a torquepulsation becomes large in plus and minus directions.

In case of an electrically-driven power steering apparatus, accordingly,a sense of incompatibility which the driver feels is intense.

On the other hand, with the electrically-driven power steering apparatusconfigured of the electric motor control apparatus illustrated inEmbodiment 4 as stated above, in the case of the abnormal state wherethe two phases undergo the interphase short-circuiting, the appearanceof the brake torque is suppressed to the utmost, and the torquepulsation can be made small. Therefore, the sense of incompatibilitywhich the driver feels can be relieved.

Besides, the electric motor control apparatus illustrated in Embodiment5 may well be employed instead of employing the electric motor controlapparatus illustrated in any of Embodiments 1-4. A case where theabnormal state of one-phase short-circuiting has occurred, will bestated below.

There will be described problems in the abnormal state where one phasein the electrically-driven power steering apparatus undergoes theshort-circuiting.

In the abnormal state of the one-phase short-circuiting, a closedcircuit is formed through a short-circuiting place and a winding havingshort-circuited, and hence, a motor rotation angle at which theappearance of a brake torque ascribable to the induced power of themotor is inevitable is existent.

The brake torque is a torque which acts in the direction of hamperingthe rotation of the motor.

When the control is performed by employing the dq control which is usedin the normal state, in the abnormal state of the one-phaseshort-circuiting, it is not suited to the abnormal state. Therefore,there are the problems that the brake torque is large, and that a torquepulsation becomes large in plus and minus directions.

In case of an electrically-driven power steering apparatus, accordingly,a sense of incompatibility which the driver feels is intense.

On the other hand, with the electrically-driven power steering apparatusconfigured of the electric motor control apparatus illustrated inEmbodiment 5 as stated above, in the case where the abnormal state ofthe one-phase short-circuiting has occurred, the appearance of the braketorque is suppressed to the utmost, and the torque pulsation can be madesmall. Therefore, the sense of incompatibility which the driver feelscan be relieved.

Besides, when the electric motor control apparatus illustrated inEmbodiment 6 is employed, a motor output can be ensured on the averageby enlarging a motor torque in an angular region in which the torque inthe plus direction is possible, so that a sense of incompatibility whichthe driver feels can be relieved.

1. An electric motor control apparatus for a multiphase AC electricmotor comprising: a current detecting circuit which detects currentsflowing through respective phases of the electric motor; current controlmeans for determining a multiphase voltage command in accordance with atorque current command corresponding to a target value of a torque to begenerated by the electric motor and detected currents flowing throughthe respective phases and detected by the current detecting circuit, thecurrent control means including normal-state current controlling meansfor controlling current in a normal state, abnormal-state currentcontrolling means for controlling current in an abnormal state,abnormal-state determining means for detecting as an abnormal phase anabnormal state of any of a wire of the electric motor, a wire of aninverter, and a wire connecting the electric motor to the inverter, andabnormal phase disconnecting means, wherein the abnormal phasedisconnecting means disconnects at least one abnormal phase detected bythe abnormal-state determining means from the circuit, and theabnormal-state current controlling means generates an abnormal-statevoltage command corresponding to the abnormal phase detected by theabnormal-state determining means and uses phases, other than adisconnected phase, of the inverter to control currents of the phases,with the abnormal-state voltage command used as the multiphase voltagecommand; and a switching element driving circuit which commands theinverter which includes switching elements, through switchingmanipulation signals, based on the multiphase voltage command from thecurrent control means, to control the switching elements of theinverter, thereby controlling currents fed to the respective phases ofthe electric motor.
 2. The electric motor control apparatus as definedin claim 1, wherein the abnormal-state determining means detects theabnormal state by estimating relative values of the detected currents ofthree or more phases, and the abnormal-state determining means detectsany phase as being in the abnormal state when a time period for which(i) magnitude of the detection current of the phase remains above apredetermined value for longer than a predetermined time period and forwhich (ii) the detected currents of other phases remain at or below apredetermined value for longer than the predetermined time period. 3.The electric motor control apparatus as defined in claim 1 wherein theabnormal-state current controlling means further includes phase currentcommand shaping means for generating phase current commands of therespective phases in accordance with the torque current command, andphase current controlling means for receiving deviations between thephase current commands from the phase current command shaping means andthe detection currents detected by the detecting circuit, and forgenerating the abnormal-state voltage command based on the currentdeviations, wherein the phase current controlling means is disposedindividually in at least one phase.
 4. The electric motor controlapparatus as defined in claim 3, wherein the phase current controllingmeans receives deviations between phase current commands from the phasecurrent command shaping means and the detection currents detected by thedetecting circuit, and generates the abnormal-state voltage command inaccordance with values obtained by additions to and/or subtractions fromthe current deviations of the normal phases and the current deviationsof the abnormal phases.
 5. The electric motor control apparatus asdefined in claim 3, wherein the abnormal-state current controlling meanscorrects the abnormal-state voltage command or abnormal-state currentcommand using at least one of rotation angular velocity and rotationangle.
 6. The electric motor control apparatus as defined in claim 1,wherein the abnormal phase disconnecting means stops operation of theswitching elements in a disabled state, in at least one of the abnormalphases, thereby disconnecting at least one of the abnormal phases fromthe circuit.
 7. The electric motor control apparatus as defined in claim1, wherein the electric motor control apparatus further comprisesrotation angle detecting means for calculating rotation angle of theelectric motor, and selective switching element disabling means forgenerating a command indicating a disabled state and supplied to theswitching elements of at least one phase, temporarily, when the rotationangle is within an angular range in which a current is to become zero.8. The electric motor control apparatus as defined in claim 1, whereinthe abnormal-state current controlling means includes dq-axis currentcommand shaping means for generating a d-axis current command and aq-axis current command in accordance with the torque current command andmotor rotation angle, and a d-axis controller and a q-axis controller towhich current deviations between the d- and q-axis current commands andd- and q-axis detection currents output from a two-phase conversionmeans are input and which generate d- and q-axis voltage commands basedon current deviations, wherein the d-axis controller and the q-axiscontroller include integral term limiting means for limiting values ofintegral terms, for integral term outputs into which outputs ofintegrators for integrating the current deviations are multiplied byintegral gains.
 9. The electric motor control apparatus as defined inclaim 1, wherein, in the abnormal state, one wire of the electric motor,one wire of the inverter, or the wire connecting the electric motor tothe inverter, short-circuits to a wire which leads to a minus potentialor a plus potential of a battery feeding electric power to the inverter,and, in response, the abnormal-state current controlling means generatesthe abnormal-state voltage command corresponding to the abnormal state.10. The electric motor control apparatus as defined in claim 1, wherein,in the abnormal state, an upper switching element or a lower switchingelement disposed in each of the phases of the inverter short-circuits,and, in response, the abnormal-state controlling means generates theabnormal-state voltage command corresponding to the abnormal state. 11.The electric motor control apparatus as defined in claim 1, wherein, inthe abnormal state, two locations of the wire of the electric motor, twolocations of the wire of the inverter, or two locations of the wireconnecting the electric motor to the inverter short-circuit, and, inresponse, the abnormal-state controlling means generates theabnormal-state voltage command corresponding to the abnormal state. 12.The electric motor control apparatus as defined in claim 1, wherein, inthe abnormal state, at least two phases short-circuit, at least one ofthe abnormal phases is disconnected by the abnormal phase disconnectingmeans, the individual phase current controlling means controlsindividual currents in the remaining phases of the inverter, and theabnormal-state voltage command or abnormal-state current command isenlarged proximate a motor rotation angle at which output torque of theelectric motor becomes zero or can be generated only in a reversedirection.
 13. An electric motor control apparatus for a multiphase ACelectric motor comprising: a current detecting circuit which detectscurrents flowing through respective phases of the electric motor;current control means for determining a multiphase voltage command inaccordance with a torque current command corresponding to a target valueof a torque to be generated by the electric motor and detected currentsflowing through the respective phases and detected by the currentdetecting circuit, the current control means including normal-statecurrent controlling means for controlling current in a normal state,abnormal-state current controlling means for controlling current in anabnormal state, abnormal-state determining means for detecting as anabnormal phase an abnormal state of any of a wire of the electric motor,a wire of an inverter, and a wire connecting the electric motor to theinverter, wherein the abnormal-state current controlling means generatesan abnormal-state voltage command corresponding to the abnormal statedetected by the abnormal-state determining means and uses both theabnormal phase and a normal phase of the inverter to control currents ofthe phases, with the abnormal-state voltage command used as themultiphase voltage command; and a switching element driving circuitwhich commands the inverter including switching elements, throughswitching manipulation signals based on the multiphase voltage commandfrom the current control means to control the switching elements of theinverter, thereby controlling currents fed to the respective phases ofthe electric motor.
 14. The electric motor control apparatus as definedin claim 13, wherein, in the abnormal state, a winding of one phase ofthe electric motor short-circuits, the individual phase currentcontrolling means controls individual currents without disconnection ofthe abnormal phases by the abnormal phase disconnecting means, and theabnormal-state voltage command or abnormal-state current command isenlarged proximate a motor rotation angle at which an induced voltage ofthe phase that is short circuited is enlarged.
 15. The electric motorcontrol apparatus as defined in claim 13, wherein the abnormal-statedetermining means detects the abnormal state by estimating relativevalues of the detected currents of three or more phases, and theabnormal-state determining means detects any phase as being in theabnormal state when a time period for which (i) magnitude of thedetection current of the phase remains above a predetermined value forlonger than a predetermined time period and for which (ii) the detectedcurrents of other phases remain at or below a predetermined value forlonger than the predetermined time period.
 16. The electric motorcontrol apparatus as defined in claim 13, wherein the abnormal-statecurrent controlling means further includes phase current command shapingmeans for generating phase current commands of the respective phases inaccordance with the torque current command, and phase currentcontrolling means for receiving deviations between the phase currentcommands from the phase current command shaping means and the detectioncurrents detected by the detecting circuit, and for generating theabnormal-state voltage command based on the current deviations, whereinthe phase current controlling means is disposed individually in at leastone phase.
 17. The electric motor control apparatus as defined in claim16, wherein the phase current controlling means receives deviationsbetween phase current commands from the phase current command shapingmeans and the detection currents detected by the detecting circuit, andgenerates the abnormal-state voltage command in accordance with valuesobtained by additions to and/or subtractions from the current deviationsof the normal phases and the current deviations of the abnormal phases.18. The electric motor control apparatus as defined in claim 16, whereinthe abnormal-state current controlling means corrects the abnormal-statevoltage command or abnormal-state current command using at least one ofrotation angular velocity and rotation angle.
 19. The electric motorcontrol apparatus as defined in claim 13, wherein the abnormal-statecurrent controlling means includes dq-axis current command shaping meansfor generating a d-axis current command and a q-axis current command inaccordance with the torque current command and motor rotation angle, anda d-axis controller and a q-axis controller to which current deviationsbetween the d- and q-axis current commands and d- and q-axis detectioncurrents output from a two-phase conversion means are input and whichgenerate d- and q-axis voltage commands based on the current deviationsand the d-axis controller and the q-axis controller include integralterm limiting means for limiting values of integral terms, for integralterm outputs into which outputs of integrators for integrating thecurrent deviations are multiplied by integral gains.
 20. The electricmotor control apparatus as defined in claim 13, wherein, in the abnormalstate, two locations of the wire of the electric motor, two locations ofthe wire of the inverter, or two locations of the wire connecting theelectric motor to the inverter short-circuit, and, in response, theabnormal-state controlling means generates the abnormal-state voltagecommand corresponding to the abnormal state.